The invention relates to a suction transport device for taking off a sheet from a sheet stack in a sheet running direction, which includes at least two revolving suction means, as well as a method for taking off sheets.
DE 26 37 073 A1 discloses a sheet feeder for folding machines in which a suction transport device is provided which includes a continuously revolving suction wheel having a horizontal axis of rotation which is transversal to the sheet running direction. By means of the suction wheel a topmost sheet on a sheet stack is grabbed and transported further to a processing machine, such as a folding machine.
In the case of suction transport devices comprising only a single suction wheel it has often been experienced that a sheet gets into a skew position, resulting in the fact that the sheet is not adequately transported further. For this reason it has become customary to provide suction transport devices with two suction wheels which are firmly installed at an equal distance from the center line of a sheet. These two suction wheels are used for all kinds of sheet sizes, from large to small. Especially in the case of very large sheets it may happen that for reasons of inertia the margins of a sheet are transported at a lower speed than the regions in which the suction wheels engage. This may lead to undesired deformation of a sheet.
The object underlying the invention is to provide a suction transport device using means of simple design by which sheets of different sizes can be reliably taken off from a sheet stack.